4-Substituted-.DELTA..sup.2 -cephalosporins are disclosed by Dolfini in U.S. Pat. No. 3,849,408. Also, various 4-thio substituted-3-acetoxy or desacetoxy-.DELTA..sup.2 -cephalosporins and methods of their preparation are disclosed in Slusarchyk et al. in German Offenlegungsschrift No. 2,453,601, (May 15, 1975).